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In 2008, the average concentration for atmospheric CO2 (Mauna Loa Observatory) was 385.57 parts per million (ppm). Based on CO2 measurements made so far, we know that the 2009 average for atmospheric CO2 is more than 387 ppm. (The seasonally-adjusted level atmospheric CO2 was 387.65 ppm in August 2009, and 388.00 ppm in September 2009.)

Since 1958, when precise CO2 measurements were first made of atmospheric air samples, the annual mean concentration of CO2 has only increased from one year to the next. There have been no decreases in annual CO2 levels since direct instrument measurements began at the Mauna Loa Observatory. The following CO2 data provides a snapshot of the longest-running, high-precision instrument record for atmospheric CO2:

Year CO2 (ppm) Notes

2009 387+ Current CO2 levels

2008 385.57 The latest year for which a full year of data is available

2007 383.71

2006 381.85

1997 363.47 Kyoto Protocol

1992 356.27 Earth Summit in Rio de Janeiro

1987 348.98 The last year in which the annual CO2 data was less than 350 ppm

1959 315.98 The first year for which a full year of precise instrument data is available